将组件加载到组件中时出现JavaFX NullPointerException

时间：2017-05-26 16:38:01

标签： javafx

我正在尝试将一些HBox添加到BorderPane的中心。当我按下按钮时，NullPointerException被打印出来。我不知道为什么，在教程应用程序中它工作。

在controllers.MainController.setCenter 在controllers.TopMenuButtonsController.todoOnAction 

public class Main extends Application {
    public static void main(String[] args) {
        launch(args);
    }
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader fxmlLoader = new FXMLLoader(this.getClass().getResource("/fxml/BorderPaneMainFXML.fxml"));
        BorderPane borderPane = fxmlLoader.load();
        Scene scene = new Scene(borderPane);
        primaryStage.setScene(scene);
        primaryStage.setTitle("TITLE");
        primaryStage.show();
    }
}



public class TopMenuButtonsController {
    @FXML 
    private MainController mainController;

    public void setMainController(MainController mainController) {
        this.mainController = mainController;
    }

    @FXML
    public void todoOnAction() {
        mainController.setCenter("/fxml/TodoFXML.fxml");

    }
}



public class MainController {
   @FXML
    public BorderPane borderPane;
   @FXML
    public TopMenuButtonsController topMenuButtonsController;
    @FXML
    public void initialize(){
        topMenuButtonsController.setMainController(this);
    }

    public void setCenter(String fxmlPatch)  {
        FXMLLoader fxmlLoader = new FXMLLoader(this.getClass().getResource(fxmlPatch));
        Parent parent = null;
        try {
            parent = fxmlLoader.load();
        } catch (IOException e) {
            e.printStackTrace();
        }
        borderPane.setCenter(parent);
    }
}



<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.layout.BorderPane?>


<?import javafx.scene.layout.VBox?>
<BorderPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="800.0" prefWidth="640.0" style="-fx-background-color: #2C3E50;" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controllers.MainController" >
    <top>
        <VBox>
            <fx:include fx:id="topMenuButtons" source="TopMenuButtons.fxml"/>
        </VBox>
    </top>


</BorderPane>


<?xml version="1.0" encoding="UTF-8"?>

<?import com.jfoenix.controls.JFXButton?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.text.Font?>

<HBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controllers.TopMenuButtonsController">
   <children>
      <JFXButton onAction="#todoOnAction" ripplerFill="#3498db" text="todo" textFill="#ecf0f1">
         <font>
            <Font name="MS Outlook" size="14.0" />
         </font></JFXButton>
      <JFXButton onAction="#gridOnAction" ripplerFill="#3497d9" text="grid" textFill="#ecf0f1">
         <font>
            <Font name="MS Outlook" size="14.0" />
         </font></JFXButton>
      <JFXButton onAction="#statsOnAction" ripplerFill="#3497d9" text="statistics" textFill="#ecf0f1">
         <font>
            <Font name="MS Outlook" size="14.0" />
         </font></JFXButton>
      <JFXButton onAction="#notesOnAction" ripplerFill="#3497d9" text="notes" textFill="#ecf0f1">
         <font>
            <Font name="MS Outlook" size="14.0" />
         </font></JFXButton>
      <JFXButton onAction="#prefOnActionn" ripplerFill="#3497d9" text="preferences" textFill="#ecf0f1">
         <font>
            <Font name="MS Outlook" size="14.0" />
         </font></JFXButton>
      <JFXButton onAction="#settingsOnAction" ripplerFill="#3497d9" text="settings" textFill="#ecf0f1">
         <font>
            <Font size="14.0" />
         </font></JFXButton>
   </children>
</HBox>


<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.HBox?>


<HBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1">
   <children>
      <Label prefHeight="136.0" prefWidth="221.0" text="Lasdfasdfsdafsdfsdbel" />
   </children>
</HBox>

<!-- language: lang-none -->

    Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
        at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
        at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
        at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
        at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
        at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
        at javafx.event.Event.fireEvent(Event.java:198)
        at javafx.scene.Node.fireEvent(Node.java:8413)
        at javafx.scene.control.Button.fire(Button.java:185)
        at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
        at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
        at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
        at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
        at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
        at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
        at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
        at javafx.event.Event.fireEvent(Event.java:198)
        at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
        at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
        at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
        at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
        at java.security.AccessController.doPrivileged(Native Method)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417)
        at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
        at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)
        at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
        at com.sun.glass.ui.View.notifyMouse(View.java:937)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
        at java.lang.Thread.run(Thread.java:745)
    Caused by: java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
        at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
        at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
        ... 48 more
    Caused by: java.lang.NullPointerException
        at controllers.MainController.setCenter(MainController.java:34)
        at controllers.TopMenuButtonsController.todoOnAction(TopMenuButtonsController.java:40)
        ... 58 more

1 个答案:

答案 0 :(得分：1)

您的<BorderPane>标记缺少fx:id属性，因此不会将其注入控制器。因此，borderPane在控制器中为空，并且在调用borderPane.setCenter(...)时会出现空指针异常。

你需要

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.layout.BorderPane?>


<?import javafx.scene.layout.VBox?>
<BorderPane fx:id="borderPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="800.0" prefWidth="640.0" style="-fx-background-color: #2C3E50;" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="controllers.MainController" >
    <top>
        <VBox>
            <fx:include fx:id="topMenuButtons" source="TopMenuButtons.fxml"/>
        </VBox>
    </top>


</BorderPane>
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